1. Field of the Invention
The present invention relates to a dishwasher, and more particularly, to a dishwasher having a steam generation unit for improving the washing performance.
2. Description of the Related Art
Generally, a dishwasher is a machine that washes and dries dishes by spraying pressurized washing water through spraying nozzles.
A typical dishwasher includes a tub defining an outer appearance of the dishwasher and a sump mounted on a floor of the tub to reserve the washing water. By the pumping operation of the washing pump mounted in the sump, the washing water is directed to the spraying nozzle and sprayed under high pressure through spraying holes formed on the spraying nozzle. The sprayed washing water collides with a surface of the dish to remove foreign objects such as food wastes adhered to the dishes. The food wastes removed from the dishes are reserved on a floor of the tub.
In order to improve the washing performance of the dishwasher, a heater is installed in the sump. When the heat is operated, the washing water is heated and sprayed into the washing tub through the spraying nozzle. By the heated washing water, the food wastes can be more effective removed from the dishes.
However, when the washing water stored in the sump is heated, the foreign objects and detergent contained in the washing water may be heated together. This causes the emission of an offensive odor. In addition, the foreign objects may be adhered to the heater. In this case, the service life of the heater may be reduced.
In addition, when a large amount of water stored in the sump is heated, the time for heating the water increase. This causes the increase of the power consumption and the energy loss.
Furthermore, when grains of boiled rice that is a staple food for most of Asia countries are adhered to the dishes, they are not easily removed from the dishes even when the heated washing water is sprayed to the dishes.